BIMA cryocooler

The BIMA cryocooler is a 3-stage Gifford-McMahon cryocooler developed at U.C. Berkeley to cool SIS (Superconductor-Insulator-Superconductor) mixers on radio telescopes. The cryocooler is basically a CTI model 1020 cold head with a third stage welded onto the end. Spheres of Er3Ni or HoCu2 (both obtained from Toshiba America Electronics) are used as the regenerator material in the third stage. The cooling capacity is roughly 50 mW at 4.2 K.

Papers describing the cryocooler: